Exemplary embodiments of the present disclosure relate to a flow guide structure for a casing flange, and a casing and a turbomachine having the same, and more particularly, to a structure reducing steam flow resistance around a casing flange and smoothing steam flow.
Generally, a turbomachine is a power generation apparatus converting a thermal energy of fluid, such as gas, steam, and the like, into a rotating force being a mechanical energy. The turbomachine typically comprises a rotor having a plurality of buckets to perform shaft rotation by the fluid and a casing installed to surround the rotor and having a plurality of diaphragms.
Herein, a gas turbine includes a compressor section, a combustor, and a turbine section. External air is inhaled and compressed by rotation of the compressor section and then sent to the combustor, and burnt by a mixture of the compressed air and fuel in the combustor. A high temperature/high pressure of gas generated in the combustor rotates the rotor of the turbine while passing through the turbine section, and thus operates a generator.
In a steam turbine, a high-pressure turbine section, an intermediate-pressure turbine section, and a low-pressure turbine section are connected serially or in parallel to rotate a rotor. In the serially connected structure, the high-pressure turbine section, the medium-pressure turbine section, and the low-pressure turbine section share one rotor. Each of turbines in the steam turbine includes a bucket and a diaphragm around a rotor inside a casing, and steam rotates the rotor while passing through the bucket and the diaphragm to thus operate a generator.
In FIG. 1, an inner casing of a low-pressure turbine inside a steam turbine is shown. Power steam passes through a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine in order, and then finally flows toward a condenser positioned at a lower end portion of the low-pressure turbine. Accordingly, the power steam discharged through a diaphragm 2 of the low-pressure turbine moves in a direction of the lower end of the low-pressure turbine.
At this time, some steam positioned at the diaphragm 2 flows along a circumference of an outer side of the inner casing from an upward direction to a downward direction. The inner casing has a structure with an upper casing 3 and a lower casing 4 coupled by flanges 5a, 5b, respectively, and almost has a stepped shape in a direction of an outer side thereof.
Consequently, steam flowing along the circumference of the outer side of the low-pressure turbine receives flow resistance at the flanges 5a, 5b around a reference numeral X, as shown in FIG. 1 and FIG. 2. The steam moving in a downward direction along the circumference of the outer side of the upper casing receives flow resistance bent by a 90-degree angle at the flange 5a around a reference numeral Y, such that a fluid velocity largely reduces and a flow direction also experiences a rapid change. Further, some turbulence occurs at a lower end portion of the flange 5b stemming from the stepped shape of the flanges 5a, 5b. 